Atomic force microscopy (AFM) is widely used in fields ranging from biophysics to surface chemistry. Through the use of mechanical and electrical feedback modes, AFM methods are used to study diverse problems such as mechanical properties and glass transitions in polymer blends, surface polarization in ferroelectrics, photogeneration of charge in solar cells, and energy storage in batteries. However, one area where AFM methods have not generally found widespread success is in the study of fast local dynamics. The fastest AFM methods typically acquire image scan lines at rates of ˜3 kHz, while studies reporting time-resolved AFM measurements with commercial instruments often measure local processes on time scales of milliseconds.
Attempts to achieve ultrafast temporal resolution with scanning probe instruments have largely employed sophisticated combinations of pulsed laser optics with either near-field scanning optical microscopy or scanning tunneling microscopy (STM). More recently, time-resolved STM methods limited to the current preamplifier bandwidth or using radio-frequency STM have been reported. These techniques can provide powerful probes in systems with suitable optical or electronic properties, but generally require complex, expensive specialty hardware and are restricted in their ability to study materials with low optical contrast or high conductivity. As a result, these probes have been limited primarily to niche applications.
What is desired, therefore, is an improved microscopy method capable of nanosecond-scale temporal resolution.